I cant take my data to usb

After i backup all my documents (which is amazingly speedy for all of my files- almost 30 gb-) to documents app of ipad:
İ cant send my data to usb
it makes a problem in last seconds everytime
i tried zip but it doesent work too
the backup file can not be send to any usb İ try …

how can we solve it
i really like to use backup all myfiles in once
because it is so speedy when i compare one and one excract from MN